Weighted average

Usually when you calculate an average, all of the numbers are given equal significance; the numbers are added together, and then, divided by the number of numbers. With a Weighted Average, one or more numbers is given a greater significance, or weight.

Find a Weighted Average

Use the SUMPRODUCT and the SUM functions to find a Weighted Average, which depends on the weight applied to the values.

For example, a shipment of 10 cases of pencils is 20 cents per case. But a second shipment of 40 cases costs 30 cents per case, because pencils are in high demand. If you averaged the cost of each shipment this way (0.20+0.30)/2 = 0.25, the result isn’t accurate.

The math doesn’t take into account that there are more cases being sold at 30 cents than at 20 cents. To get the correct average, use this formula to get the result (28 cents per shipment):

=SUMPRODUCT(A2:A3,B2:B3)/SUM(B2:B3)

The formula works by dividing the total cost of the two orders by the total number of cases ordered.